#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int i = 0;
	double sum1 = 0.0;
	double sum2 = 0.0;
	double sum = 0.0;
	for (i = 1; i <= 100; i++)
	{
		if ((i % 2) == 0)
			sum1 = 1.0 / i + sum1;
		else 
			sum2 = 1.0 /i + sum2;
	}
	sum = sum2-sum1;
	printf("%lf", sum);
	return 0;
}